An Analytical Study on an Orthodontic Index: Index of Complexity, Outcome and Need (ICON)

Statement of the Problem The validity of the Index of Complexity, Outcome and Need (ICON) which is an orthodontic index developed and introduced in 2000 should be studied in different ethnic groups. Purpose The aim of this study was to perform an analysis on the ICON and to verify whether this index is valid for assessing both the need and complexity of orthodontic treatment in Iran. Materials and Method Five orthodontists were asked to score pre-treatment diagnostic records of 100 patients with a uniform distribution of different types of malocclusions determined by Dental Health Component of the Index of Treatment Need. A calibrated examiner also assessed the need for orthodontic treatment and complexity of the cases based on the ICON index as well as the Index of Orthodontic Treatment Need (IOTN). 10 days later, 25% of the cases were re-scored by the panel of experts and the calibrated orthodontist. Results The weighted kappa revealed the inter-examiner reliability of the experts to be 0.63 and 0.51 for the need and complexity components, respectively. ROC curve was used to assess the validity of the index. A new cut-off point was adjusted at 35 in lieu of 43 as the suggested cut-off point. This cut-off point showed the highest level of sensitivity and specificity in our society for orthodontic treatment need (0.77 and 0.78, respectively), but it failed to define definite ranges for the complexity of treatment. Conclusion ICON is a valid index in assessing the need for treatment in Iran when the cut-off point is adjusted to 35. As for complexity of treatment, the index is not validated for our society. It seems that ICON is a well-suited substitute for the IOTN index.


Introduction
The demand for orthodontic treatment has increased over the last decade in Iran as well as other countries along with an increase in general awareness of esthetics. [1] Policy making for orthodontic treatment and designating human and financial resources is only possible when accurate epidemiologic studies are carried out in the society and treatment needs are well clarified.
Although there is not a universally accepted measure for assessment of orthodontic treatment need, [2] different indices have developed over the years for an objective measurement of the need for orthodontic treatment. Recently, a new index has been developed that assesses the need for treatment, treatment complexity and outcome and is based on the general consensus of 97 orthodontists across the globe which is called the Index of Complexity, Outcome and Need (ICON). [3] It has been developed by Daniels and Richmond [3] in 2000 and is claimed to be simpler to assess than previously introduced indices. Since this index has been invented, its reliability and validity has been assessed in some ethnic groups [1,[4][5][6][7] and is yet to be evaluated in other racial groups. The cut-off value originally assigned by Daniels and Richmond was concluded not to be appropriate in a Dutch population and a higher value was suggested. [4] But it seemed to be reliable when assessed by calibrated orthodontists. Even though the need for orthodontic treatment has been evaluated using the ICON score in some ethnic groups, [4][5][6][7] the importance of validating this index is still in debate before it can be employed as an extensive epidemiologic assessment tool in Iran. A new diagnostic method can be validated when it is compared with the gold standard which is the common sense of orthodontists in the case. [4][5][6] The aims of this study were to assess the validity of the need for orthodontic treatment and complexity of treatment in the ICON index and to compare the level of agreement between the IOTN and ICON indices.

Materials and Method
In order to select the study sample, orthodontic diagnostic records of 650 patients at the Orthodontic Department, Shiraz University of Medical Sciences were collected. The Dental Health Component (DHC) of the IOTN index of all the samples was measured and eventually 100 cases were selected that represented different types of malocclusion. Therefore, no randomization was carried out; instead a uniform study sample was provided. The selection was conducted to eventually have equal cases of different classes of malocclusion.
Panoramic radiographs, lateral cephalograms, and extraoral photographs as well as the study casts of the patients were collected as the diagnostic records.
Panoramic radiograph were used to determine impactions, missing or blocked out teeth. All the records were either photographed or scanned and then imported into the PowerPoint software and consecutive slides were made from the diagnostic records of each patient.
Five volunteer orthodontists were invited to score the cases. The inclusion criteria for the expert panel were a minimum experience of 5 years in clinical practice and willingness to take part in the study. seek each other's opinions during the session. There was no time limit in filling out the form but each orthodontist was asked to fill the form in a single session. The resulting scores obtained from the orthodontists were called the 'clinical sense'. The participants were then asked to indicate which score they believe could represent the cut-off point above which the orthodontic treatment was definitely required for each patient. This was called the Indicated Treatment Point (ITP). [4] The view of the majority of the raters determined the gold standard. Therefore, if more than 3 raters gave a certain score to a patient, the gold standard would be set to that number, providing the most popular opinion.
10 days later, 30 of the casts were randomly selected from the study sample to evaluate intraexaminer reliability and were displayed once more for the orthodontists to be scored via the same method.
One calibrated orthodontist evaluated and scored All the obtained data was imported into the SPSS software version 9.1 (IBM Corporation). Simple kappa and weighted kappa tests were used to assess interexaminer and intra-examiner reliability via the WinPepi software version 3.8.
[9] ROC curve was used to evaluate the validity of the ICON index by moving the boundaries to find the best threshold in our society.

Results
The IOTN was measured in all the cases (n= 100) prior to assessment by the panel in order to ensure a wide variety of cases based on the severity of malocclusions were included in the sample. Distribution of different types of malocclusion based on DHC is outlined in Table 1.  When the intra-examiner reliability of the calibrated orthodontist was assessed, the kappa coefficient showed almost perfect agreement (kappa= 0.82, p< 0.00). After dichotomizing the results as "no treatment need" and "treatment required", the intra-examiner reliability for the calibrated examiner was still "almost perfect" (kappa=0.89, p< 0.00).In order to evaluate the validity of ICON index in assessing the need for treatment, the sensitivity and specificity of ICON index at different cuff-off points was evaluated using the ROC curve. It was shown that the best cut-off point in our community for definite treatment need was 35.5 in lieu of 43 ( Figure 1 and Table 3).

Conclusion
In terms of orthodontic treatment need, there was substantial agreement between the gold standard and the ICON index and thus the ICON index seems to be a viable candidate to substitute the IOTN index. ICON is a valid index in assessing the need for orthodontic treatment in Iran when the cut-off point is adjusted to 35. When the cut-off point was adjusted to 35 in lieu of 43, the highest level of sensitivity and specificity can be obtained for our society. The complexity component of the index was not validated in our country.
Therefore, thus far, there is not a validated index for assessing the complexity of orthodontic treatment in our society.